--- Some code taken from [AoC 2017 day 5](https://adventofcode.com/2017/day/5),
--- and some from [AoC 2018 day 21](https://adventofcode.com/2018/day/21)
-
import Data.Text (Text)
import qualified Data.Text.IO as TIO
import Data.List (foldl')
import qualified Data.Set as S
+import qualified Data.Map as M
+import Data.Map ((!))
import Linear (V2(..), (^+^), (^-^), (*^), (*^))
type Visited = S.Set Location
-data Path = Path { _visited :: Visited
+type TrackedVisited = M.Map Location Int
+
+data Path = Path { _visited :: TrackedVisited
, _tip :: Location
+ , _currentLength :: Int
}
deriving (Show, Eq)
main = do
text <- TIO.readFile "data/advent03.txt"
let segmentss = successfulParse text
- print segmentss
+ let paths = travelAllPaths segmentss
-- print $ travelPath $ head segmentss
- print $ part1 segmentss
- -- print $ part2 machine
+ print $ part1 paths
+ print $ part2 paths
+
+part1 :: [Path] -> Int
+part1 paths = closest $ crossovers paths
+
+part2 :: [Path] -> Int
+part2 paths = shortestPaths paths $ crossovers paths
-part1 :: [[Segment]] -> Int
-part1 segmentss = closest $ crossovers $ travelAllPaths segmentss
closest :: Visited -> Int
closest points = S.findMin $ S.map manhattan points
+
+shortestPaths :: [Path] -> Visited -> Int
+shortestPaths paths crossings = minimum $ S.map crossingPathLengths crossings
+ where crossingPathLengths crossing = sum $ map (\p -> (_visited p)!crossing) paths
+
+
crossovers :: [Path] -> Visited
crossovers travelledPaths =
foldl' S.intersection
- (_visited $ head travelledPaths)
- (map _visited $ drop 1 travelledPaths)
+ (M.keysSet $ _visited $ head travelledPaths)
+ (map (M.keysSet . _visited) $ drop 1 travelledPaths)
travelAllPaths :: [[Segment]] -> [Path]
travelAllPaths = map travelPath
travelPath :: [Segment] -> Path
travelPath segments = foldl' travelSegment path0 segments
- where path0 = Path { _visited = S.empty, _tip = V2 0 0 }
+ where path0 = Path { _visited = M.empty, _tip = V2 0 0, _currentLength = 0 }
travelSegment :: Path -> Segment -> Path
-travelSegment path segment = path { _tip = tip', _visited = visited' }
+travelSegment path segment = path { _tip = tip', _visited = visited', _currentLength = len'}
where delta = facing $ _direction segment
distance = _steps segment
start = _tip path
+ len = _currentLength path
+ len' = len + distance
visited = _visited path
- visited' = foldl' (flip S.insert) visited $ take distance $ drop 1 $ iterate (^+^ delta) start
+ visited' = foldl' insertStep visited $ take distance $ drop 1 $ zip [len, (len + 1) ..] $ iterate (^+^ delta) start
tip' = start ^+^ distance *^ delta
+ insertStep visits (dist, loc) = if loc `M.member` visits
+ then visits
+ else M.insert loc dist visits
facing :: Direction -> Location
facing East = V2 1 0
--- /dev/null
+import Data.Text (Text)
+import qualified Data.Text.IO as TIO
+
+import Data.Void (Void)
+
+import Text.Megaparsec hiding (State)
+import Text.Megaparsec.Char
+import qualified Text.Megaparsec.Char.Lexer as L
+import qualified Control.Applicative as CA
+
+import Data.List (foldl')
+import qualified Data.Set as S
+
+import Linear (V2(..), (^+^), (^-^), (*^), (*^))
+
+data Direction = East | South | West | North deriving (Show, Eq)
+
+type Location = V2 Int -- x, y
+
+type Visited = S.Set Location
+
+data Path = Path { _visited :: Visited
+ , _tip :: Location
+ }
+ deriving (Show, Eq)
+
+data Segment = Segment { _direction :: Direction
+ , _steps :: Int
+ } deriving (Show, Eq)
+
+
+main :: IO ()
+main = do
+ text <- TIO.readFile "data/advent03.txt"
+ let segmentss = successfulParse text
+ -- print segmentss
+ -- print $ travelPath $ head segmentss
+ print $ part1 segmentss
+ -- print $ part2 machine
+
+part1 :: [[Segment]] -> Int
+part1 segmentss = closest $ crossovers $ travelAllPaths segmentss
+
+closest :: Visited -> Int
+closest points = S.findMin $ S.map manhattan points
+
+crossovers :: [Path] -> Visited
+crossovers travelledPaths =
+ foldl' S.intersection
+ (_visited $ head travelledPaths)
+ (map _visited $ drop 1 travelledPaths)
+
+travelAllPaths :: [[Segment]] -> [Path]
+travelAllPaths = map travelPath
+
+travelPath :: [Segment] -> Path
+travelPath segments = foldl' travelSegment path0 segments
+ where path0 = Path { _visited = S.empty, _tip = V2 0 0 }
+
+travelSegment :: Path -> Segment -> Path
+travelSegment path segment = path { _tip = tip', _visited = visited' }
+ where delta = facing $ _direction segment
+ distance = _steps segment
+ start = _tip path
+ visited = _visited path
+ visited' = foldl' (flip S.insert) visited $ take distance $ drop 1 $ iterate (^+^ delta) start
+ tip' = start ^+^ distance *^ delta
+
+facing :: Direction -> Location
+facing East = V2 1 0
+facing South = V2 0 (-1)
+facing West = V2 (-1) 0
+facing North = V2 0 1
+
+
+manhattan (V2 x y) = (abs x) + (abs y)
+
+-- Parse the input file
+type Parser = Parsec Void Text
+
+sc :: Parser ()
+sc = L.space (skipSome spaceChar) CA.empty CA.empty
+-- sc = L.space (skipSome (char ' ')) CA.empty CA.empty
+
+lexeme = L.lexeme sc
+integer = lexeme L.decimal
+-- signedInteger = L.signed sc integer
+symb = L.symbol sc
+comma = symb ","
+
+wiresP = some pathP
+pathP = segmentP `sepBy1` comma
+
+segmentP = segmentify <$> directionP <*> integer
+ where segmentify direction steps =
+ Segment { _direction = direction, _steps = steps }
+
+
+directionP = eP <|> sP <|> wP <|> nP
+eP = (symb "R" *> pure East)
+sP = (symb "D" *> pure South)
+wP = (symb "L" *> pure West)
+nP = (symb "U" *> pure North)
+
+
+successfulParse :: Text -> [[Segment]]
+successfulParse input =
+ case parse wiresP "input" input of
+ Left _err -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err
+ Right wires -> wires
\ No newline at end of file
projects / advent-of-code-19.git / commitdiff